This application details a proposal for a prospective longitudinal panel study with a random sample of 360 individuals attending alternative to incarceration (ATI) programs in New York City (NYC) that serve drug- involved offenders. The proposed study focuses on (1) the impact of utilization of formal healthcare and psychosocial services on outcomes of ATI program completion, recidivism, technical violations (i.e., law- breaking behaviors not resulting in re-incarceration), and pro-social change (e.g., fulfilling child- and elder- caretaking roles); and (2) factors affecting service utilization among ATI program participants. The study fulfills several recommendations from the Blue Ribbon Task Force on Health Service Research at NIDA, including broadening both (a) the venues of drug abuse services researchto include programs in "nontraditional" settings, especially the criminal justice system, and (b) the range of needs and characteristics of subgroups that are studied in order to address a fuller "continuum of care and patient groups." The Task Force's recommendations echoed other calls regarding the need to elucidate mediators of success of treatment, especially those in nontraditional settings such as criminal justice programs for drug-involved offenders.Also consistent with the Task Force report, the proposed research will employ new data analysis methods for causal inference using observational data. The significance and feasibility of the proposed study are substantiated by findings from a pilot study successfully completed by the investigators. For the proposed study, we will recruit individuals at the start of their participation in ATI programs designed for adult, drug-involved offenders in NYC, conducting structured interviews every 3 months over the course of 18 months for each participant. Aims, hypotheses, and measurements are guided by the Network Episode Model, an innovative model that conceptualizes access and attendance of formal services as a time-varying behavior driven by level of need and shaped by dynamic processes involving individual/social context factors and service system experiences. The proposed study is designed to achieve the following primary aims: (1) To examine the causal relationship between service utilization and (a) ATI program completion, (b) recidivism, (c) technical violations, and (d) pro-social change; and (2) To identify and estimate the causal impact of factors that influence access and utilization of formal services among ATI participants. Findings will generate substantive and practical implications for researchers and professionals in the areas of drug abuse, services research, criminal justice, and public health in developing and testing future interventions and programs for drug-involved offenders. The proposed study will be conducted by Dr. Elwin Wu and Dr. Nabila EI-Bassel of the Social Intervention Group at the Columbia University School of Social Work.